[1] Field of the Invention
The present invention generally relates to an ionizer that is used for diselectrifying a workpiece that is electrified with a positive electric charge or a negative electric charge, that is, an ionizer that is used for the electrical neutralization thereof. In particular, the invention relates to an ionizer having a mechanism for cleaning discharge electrodes that generate positive ions and negative ions by means of corona discharge. An ionizer to which the invention is directed makes it possible for a user to clean such discharge electrodes with the use of a pair of cleaning members, or at least one cleaning member, when they are not clean.
[2] Description of the Related Art
An ionizer that utilizes corona discharge is used in the work-processing steps of various kinds of workpieces such as a semiconductor wafer, a liquid crystal glass, and the like in order to electrically neutralize a workpiece that is charged positively and negatively with static electricity (i.e., destaticization). Ionizers utilizing corona discharge can be roughly classified into direct current (DC) ionizers and alternating current (AC) ionizers. For example, a DC ionizer has positive discharge electrodes and negative discharge electrodes that have a needle-like tip shape. Through the application of a positive high voltage to the positive discharge electrodes and the application of a negative high voltage to the negative discharge electrodes, corona discharge is generated at the discharging part of each of the discharge electrodes, which is the front-end part thereof. Positive ions and negative ions are generated due to the corona discharge. The generated positive and negative ions are blown on a workpiece, which is the target of diselectrification, with the use of a flow of destaticizing air. By this means, the DC ionizer neutralizes a positive electric charge and a negative electric charge on the target workpiece. On the other hand, an AC ionizer applies an alternating voltage to discharge electrodes so that positive ions and negative ions are generated alternately from the discharge electrodes.
In such a typical ionizer of related art, when corona discharge is generated at discharge electrodes, dust particles suspended in the air are attracted to the discharging parts of the discharge electrodes. As dust settles thereon and adheres thereto, the discharging parts of the discharge electrodes become insulated gradually. The gradual insulation of the discharging parts of the discharge electrodes makes it harder to generate corona discharge, which obstructs ion generation. If the generation of ion is obstructed, the diselectrification efficiency of the ionizer decreases. In order to avoid the deterioration of the destaticization performance of the ionizer, it is necessary to clean the discharging parts of discharge electrodes thereof periodically with the use of a cleaning member such as a brush or the like. If a separate cleaning member that does not constitute a part of the ionizer is provided/used for cleaning, a user might forget to keep the cleaning member for the next use, or the cleaning member may be lost.
In order to overcome such a problem, an ionizer that is provided with a cleaning member (brush member) in addition to discharge electrodes and a fan inside the air-blow hole of a case has been proposed in the art as described in Japanese Unexamined Patent Application Publication No. 2004-234972. The ionizer described in Japanese Unexamined Patent Application Publication No. 2004-234972 is provided with a movable member that turns when driven by the flow of air that is supplied from the fan inside the air-blow hole. The cleaning member is mounted on the movable member. When the cleaning member turns together with the movable member, it is brought into contact with the front-end parts of the discharge electrodes one after another. As a result, the cleaning member sweeps dust particles off the front-end parts thereof.
However, the ionizer described in Japanese Unexamined Patent Application Publication No. 2004-234972 has the following disadvantages. Since the movable member and the cleaning member are provided inside the air-blow hole, the movable member and the cleaning member shut off or disturb the flow of air containing ions, which results in a decrease in air-blowing efficiency. In addition, ion recombination occurs due to the mixture of positive ions and negative ions, which is caused by the disturbance of air. If ion recombination occurs, the amount of ion that reaches a diselectrification target workpiece decreases.
Moreover, the ionizer described in the publication identified above has the following disadvantages. Since the cleaning of the discharge electrodes is conducted during the operation of the ionizer, dust particles that have been swept off the discharging parts of the discharge electrodes are scattered by the flow of air. The scattered dust particles could re-adhere to other part of the ionizer. Or, the scattered dust particles could flow out of the ionizer and contaminate a diselectrification environment. Or, the scattered dust particles could be blown to a diselectrification target workpiece and make it unclean.